Injection moldable silicone composition

Abstract

An injection moldable composition, comprising: A) a silicone resin (I) [R13SiO1/2]a[R2R3SiO2/2]b[SiO4/2]c, wherein R1, R2, and R3 are hydrocarbyl, hydrocarbyloxy, or hydroxyl, at least one of R2 or R3 is alkenyl, subscripts a, b, and c are each >0 and a+b+c=1, B) 0 to 90% (w/w), based on the weight of A) and B), of a silicone resin (II) [R43SiO1/2]d[SiO4/2]e wherein R4 is hydrocarbyl, hydrocarbyloxy, or hydroxyl, at least one of R4 is alkenyl, subscripts d and e are each >0, and d+e=1, C) a siloxane polymer having formula (III), [R53SiO1/2]fR6R7SiO2/2]g. wherein R5-7 are hydrocarbyl or hydroxyl, at least one of R5-7 is alkenyl, subscripts f and g are each >0, and f+g=1, D) a silicone crosslinker having at least two silicon-bonded hydrogen atoms per molecule, and E) a hydrosilylation catalyst, wherein the ratio of silicon-bonded hydrogen atoms to carbon-carbon double bonds is from 1.2 to 2.2.

That which is claimed is: 
     
       1. An injection moldable silicone composition, comprising:
 A) a silicone resin having an average formula (I)
   [R 1   3 SiO 1/2 ] a [R 2 R 3 SiO 2/2 ] b [SiO 4/2 ] c ,  (I)
 
 
 wherein each R 1 , R 2 , and R 3  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 2  or R 3  is alkenyl, and subscripts a, b, and c are each >0 and a+b+c=1, 
 B) 0 to 90% (w/w), based on the weight of A) and B), of a silicone resin having the average formula (II)
   [R 4   3 SiO 1/2 ] d [SiO 4/2 ] e ,  (II)
 
 
 wherein each R 4  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 4  is alkenyl, and subscripts d and e are each >0, and d+e=1, 
 C) a siloxane polymer having an average formula (III)
   [R 5   3 SiO 1/2 ] f [R 6 R 7 SiO 2/2 ] g ,  (III)
 
 
 wherein each R 5-7  are independently hydrocarbyl having from 1 to 10 carbon atoms or hydroxyl, and at least one of R 5-7  is alkenyl, and subscripts f and g are each >0, and f+g=1 
 D) a silicone crosslinker having at least two silicon-bonded hydrogen atoms per molecule wherein the crosslinker is according to formula (IV)
   [R 8   3 SiO 1/2 ] h [R 8   2 SiO 2/2 ] i [R 10 SiO 3/2 ] j [SiO 4/2 ] k ,  (IV)
 
 
 wherein each R 8  is independently hydrocarbyl or hydrogen, each R 9  is independently hydrocarbyl having from 1 to 10 carbon atoms, each R 10  is independently hydrocarbyloxy or hydroxyl, subscripts h+i+j+k=1, h>0, k>0, i≥0, j≥0, and 
 E) a hydrosilylation catalyst, 
 wherein the ratio of silicon-bonded hydrogen atoms to carbon-carbon double bonds is from 1.2 to 2.2. 
 
     
     
       2. A composition according to  claim 1 , further comprising an inhibitor. 
     
     
       3. A composition according to  claim 2 , wherein the inhibitor is a branched, unsaturated alcohol having from 4 to 10 carbon atoms. 
     
     
       4. A composition according to  claim 1 , wherein each R 1  is independently methyl or hydroxyl, each R 2  is independently vinyl or methyl, each R 3  is methyl, each R 4  is independently vinyl or hydroxyl, and each R 5  is independently vinyl, methyl, or hydroxyl, and wherein the ratio of silicon-boned hydrogen atoms to carbon-carbon double bonds is from 1.5 to 2.2. 
     
     
       5. A composition according to  claim 1 , wherein R 8  represents two methyl groups and hydrogen, subscripts j=0 and i=0. 
     
     
       6. A composition according to  claim 1 , wherein the hydrosilylation catalyst comprises a compound of platinum. 
     
     
       7. A method for injection molding a composition, the method comprising:
 injecting an injection moldable silicone composition comprising
 A) a silicone resin having an average formula (I)
   [R 1   3 SiO 1/2 ] a [R 2 R 3 SiO 2/2 ] b [SiO 4/2 ] c ,  (I)
 
 
 wherein each R 1 , R 2 , and R 3  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 2  or R 3  is alkenyl, and subscripts a, b, and c are each >0 and a+b+c=1, 
 B) 0 to 90% (w/w), based on the weight of A) and B), of a silicone resin having the average formula (II)
   [R 4   3 SiO 1/2 ] d [SiO 4/2 ] e ,  (II)
 
 
 wherein each R 4  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 4  is alkenyl, and subscripts d and e are each >0, and d+e=1, 
 C) a siloxane polymer having an average formula (III)
   [R 5   3 SiO 1/2 ] f [R 6 R 7 SiO 2/2 ] g ,  (III)
 
 
 wherein each R 5-7  are independently hydrocarbyl having from 1 to 10 carbon atoms or hydroxyl, and at least one of R 5-7  is alkenyl, and subscripts f and g are each >0, and f+g=1 
 D) a silicone crosslinker having at least two silicon-bonded hydrogen atoms per molecule, and 
 E) a hydrosilylation catalyst, 
 into a mold and subjecting the injected moldable composition to conditions sufficient to cure the injected moldable composition. 
 
 
     
     
       8. An injection molded article comprising:
 an article produced by injection molding an injection moldable silicone composition comprising
 A) a silicone resin having an average formula (I)
   [R 1   3 SiO 1/2 ] a [R 2 R 3 SiO 2/2 ] b [SiO 4/2 ] c ,  (I)
 
 
 wherein each R 1 , R 2 , and R 3  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 2  or R 3  is alkenyl, and subscripts a, b, and c are each >0 and a+b+c=1, 
 B) 0 to 90% (w/w), based on the weight of A) and B), of a silicone resin having the average formula (II)
   [R 4   3 SiO 1/2 ] d [SiO 4/2 ] e ,  (II)
 
 
 wherein each R 4  is independently hydrocarbyl having from 1 to 10 carbon atoms, hydrocarbyloxy having from 1 to 10 carbon atoms, or hydroxyl, and at least one of R 4  is alkenyl, and subscripts d and e are each >0, and d+e=1, 
 C) a siloxane polymer having an average formula (III)
   [R 5   3 SiO 1/2 ] f [R 6 R 7 SiO 2/2 ] g ,  (III)
 
 
 wherein each R 5-7  are independently hydrocarbyl having from 1 to 10 carbon atoms or hydroxyl, and at least one of R 5-7  is alkenyl, and subscripts f and g are each >0, and f+g=1 
 D) a silicone crosslinker having at least two silicon-bonded hydrogen atoms per molecule, and 
 E) a hydrosilylation catalyst.